The Kai-Protein Clock—Keeping Track of Cyanobacteria’s Daily Life

Snijder, Joost; Axmann, Ilka M.

doi:10.1007/978-3-030-28151-9_12

Cited by 6 publications

(5 citation statements)

References 150 publications

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“…Evolutionary studies imply an intricate link between the origin of kaiA and the evolution of aerobic diazotrophic cyanobacteria 9,43 . Evidence based on phylogenetic analysis suggest that cyanobacteria rst emerged as anaerobic diazotrophs more than 3 billion years ago and subsequently evolved into microaerobic diazotrophs that relied on temporal separation of photosynthesis and nitrogen xation 44,45 .…”

Section: Discussionmentioning

confidence: 99%

KaiA regulates intracellular oxygen dynamics in unicellular diazotrophic cyanobacteria

Bandyopadhyay

Sengupta

Pakrasi

2023

Preprint

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The discovery of nitrogen fixation in unicellular cyanobacteria provided the first clues for the existence of a circadian clock in prokaryotes. However, recalcitrance to genetic manipulation barred their use as model systems for deciphering the clock function. Here, we explore the circadian clock in the now genetically amenable Cyanothece 51142, a unicellular, nitrogen-fixing cyanobacterium. Unlike non-diazotrophic clock models, Cyanothece 51142 exhibits conspicuous self-sustained rhythms in various discernable phenotypes, offering a platform to directly study the effects of the clock on the physiology of an organism. Deletion of kaiA in this strain impacted regulation of oxygen cycling and hindered nitrogenase activity. Our findings imply a role for KaiA in regulating the intracellular oxygen dynamics in unicellular diazotrophic cyanobacteria and suggest that its addition to the KaiBC clock was likely an adaptive strategy that ensured optimal nitrogen fixation as microbes evolved from an anaerobic to an aerobic atmosphere under nitrogen constraints.

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Section: Discussionmentioning

confidence: 99%

KaiA regulates intracellular oxygen dynamics in unicellular diazotrophic cyanobacteria

Bandyopadhyay

Sengupta

Pakrasi

2023

Preprint

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“…The circadian clock of Synechococcus elongatus , a model organism in the study of cyanobacterial circadian rhythms, relies on Kai proteins (i.e., KaiA, KaiB, and KaiC), forming a core oscillator that synchronizes with environmental signals and controls gene expression [ 4 , 5 ]. For a more in-depth understanding of the KaiABC oscillator’s functioning and its regulatory network, please refer to reviews Cohen & Golden [ 6 ]; Swan and colleagues [ 7 ]; Snijder & Axmann [ 8 ]. The composition and functioning of Kai systems in Cyanobacteria exhibit significant variation, albeit being less extensively documented [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

Diel Cycle Proteomics: Illuminating Molecular Dynamics in Purple Bacteria for Optimized Biotechnological Applications

Matallana-Surget,

Geron,

Decroo

et al. 2024

IJMS

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Circadian rhythms, characterized by approximately 24 h cycles, play a pivotal role in enabling various organisms to synchronize their biological activities with daily variations. While ubiquitous in Eukaryotes, circadian clocks remain exclusively characterized in Cyanobacteria among Prokaryotes. These rhythms are regulated by a core oscillator, which is controlled by a cluster of three genes: kaiA, kaiB, and kaiC. Interestingly, recent studies revealed rhythmic activities, potentially tied to a circadian clock, in other Prokaryotes, including purple bacteria such as Rhodospirillum rubrum, known for its applications in fuel and plastic bioproduction. However, the pivotal question of how light and dark cycles influence protein dynamics and the expression of putative circadian clock genes remains unexplored in purple non-sulfur bacteria. Unraveling the regulation of these molecular clocks holds the key to unlocking optimal conditions for harnessing the biotechnological potential of R. rubrum. Understanding how its proteome responds to different light regimes—whether under continuous light or alternating light and dark cycles—could pave the way for precisely fine-tuning bioproduction processes. Here, we report for the first time the expressed proteome of R. rubrum grown under continuous light versus light and dark cycle conditions using a shotgun proteomic analysis. In addition, we measured the impact of light regimes on the expression of four putative circadian clock genes (kaiB1, kaiB2, kaiC1, kaiC2) at the transcriptional and translational levels using RT-qPCR and targeted proteomic (MRM-MS), respectively. The data revealed significant effects of light conditions on the overall differential regulation of the proteome, particularly during the early growth stages. Notably, several proteins were found to be differentially regulated during the light or dark period, thus impacting crucial biological processes such as energy conversion pathways and the general stress response. Furthermore, our study unveiled distinct regulation of the four kai genes at both the mRNA and protein levels in response to varying light conditions. Deciphering the impact of the diel cycle on purple bacteria not only enhances our understanding of their ecology but also holds promise for optimizing their applications in biotechnology, providing valuable insights into the origin and evolution of prokaryotic clock mechanisms.

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“…The active form of KaiC is a hexamer (Pattanayek et al, 2004; Xu et al, 2004); it is endowed with ATPase activity and can autophosphorylate at, at least, two residues (a serine, S431, and a threonine, T432), thereby generating four phosphorylation variants (S/T, S~P/T, S~P/T~P, S/T~P). KaiC alternates between autokinase and autophosphatase activities depending on its interactants (Snijder & Axmann, 2019). In consequence of this dynamics, the relative abundance of the four KaiC phosphorylation variants oscillates in a ~24‐h cycle both in vivo and in vitro.…”

Section: Introductionmentioning

confidence: 99%

KaiC‐like proteins contribute to stress resistance and biofilm formation in environmental Pseudomonas species

Terrettaz

Cabete

Geiser

et al. 2023

Environmental Microbiology

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KaiC is the central cog of the circadian clock in Cyanobacteria. Close homologues of this protein are widespread among nonphotosynthetic bacteria, but the function, interaction network, and mechanism of action of these proteins are still largely unknown. Here, we focus on KaiC homologues found in environmental Pseudomonas species. Using bioinformatics, we describe the distribution of this protein family in the genus and reveal a conserved interaction network comprising a histidine kinase and response regulator. We characterize experimentally the only KaiC homologue present in Pseudomonas putida KT2440 and Pseudomonas protegens CHA0. Through phenotypic assays and transcriptomics, we show that KaiC is involved in osmotic and oxidative stress resistance in P. putida and in biofilm production in both species. KaiC homologues are found in different phosphorylation states and physically interact with a cognate histidine kinase and response regulator. In contrast with cyanobacterial counterparts, the expression and phosphorylation of KaiC homologues do not correlate with light variations under 12:12 light: dark cycles in either Pseudomonas species, and KaiC itself is not required to support a light‐driven behaviour in P. putida. Overall, this suggests that KaiC homologues in Pseudomonas species are involved in environmental stress resistance but not in responses to diurnal rhythms.

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The Kai-Protein Clock—Keeping Track of Cyanobacteria’s Daily Life

Cited by 6 publications

References 150 publications

KaiA regulates intracellular oxygen dynamics in unicellular diazotrophic cyanobacteria

KaiA regulates intracellular oxygen dynamics in unicellular diazotrophic cyanobacteria

Diel Cycle Proteomics: Illuminating Molecular Dynamics in Purple Bacteria for Optimized Biotechnological Applications

KaiC‐like proteins contribute to stress resistance and biofilm formation in environmental Pseudomonas species

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